Fiber reinforced thermoplastics have a light weight and an excellent strength. In the fiber reinforced thermoplastics, long fiber reinforced thermoplastics, which includes a reinforcing fiber with a long fiber length, has a particularly excellent impact resistance or rigidity. The long fiber reinforced thermoplastic is used in a form of a string shape for, for example, a gut of a tennis racket or the like.
A long fiber reinforced plastic strand is obtained by forming the long fiber reinforced thermoplastic in a string shape. Hitherto, a production device disclosed in Patent Document 1 has been known as a device for producing a long fiber reinforced plastic strand wound on a bobbin by winding up a long fiber reinforced plastic strand on a winding-up bobbin. FIG. 3 illustrates a configuration of a main part of the production device of the related art. The production device of the related art will be described by referring to FIG. 3.
In FIG. 3, an impregnation head (cross head) 105 is provided. The impregnation head 105 is used to simultaneously impregnate, with a molten thermoplastic, a plurality of reinforcing fiber bundles continuously introduced from a plurality of fiber supply units (supply bobbins) (not illustrated) into the impregnation head 105. A shaping die 109 is attached to the exit end for deriving the fiber bundle which has been impregnated with the plastic from the inside of the impregnation head 105 in the impregnation head 105. Further, a cooling machine (cooling water bath) 110 is provided at the downstream side of the impregnation head 105 and the shaping die 109 in the fiber bundle sending direction. Further, a winding-up machine 118 which includes an arm portion 114, a rotation shaft 115, and a winding-up reel 117 is provided at the downstream side of the cooling machine 110. In the winding-up machine 118, the rotation shaft 115 is positioned on the extension line of the path line as the line along which the fiber bundle passing through the shaping die 109 flows from the impregnation head 105. Then, the winding-up reel 117 is configured to rotate, and is connected to the rotation shaft 115 through the arm portion 114. Further, in FIG. 3, guide rolls 116a and 116b are provided. The guide rolls 116a and 116b are used to assist the movement of the long fiber reinforced plastic strand 113 in the length direction thereof.
In the production device of the related art, the winding-up machine 118 with the above-described configuration twists the reinforcing fiber bundle which has been impregnated with the plastic in a manner that the reinforcing fiber bundle is rotated about its axis (a long axis) while the reinforcing fiber bundle which has been impregnated with the plastic is drawn out from the impregnation head 105. Accordingly, the long fiber reinforced plastic strand 113 is formed. Further, in the production device of the related art, the twisted long fiber reinforced plastic strand 113 is cooled and solidified by a cooling machine 110, and the cooled and solidified long fiber reinforced plastic strand 113 is wound up on the winding-up reel 117.
However, in the production device of the related art, since the winding-up machine 118 may twist the reinforcing fiber bundle which has been impregnated with the plastic and haul off the twisted long fiber reinforced plastic strand to directly wind up the twisted long fiber reinforced plastic strand thereon, the long fiber reinforced plastic strand which has a torsional elastic deformation caused by the twisting is directly wound on the winding-up reel 117. For this reason, when the long fiber reinforced plastic strand is drawn out from the long fiber reinforced plastic strand wound on the bobbin, torsion is generated in the drawn long fiber reinforced plastic strand. As a result, a problem arises in that the long fiber reinforced plastic strand may not be easily handled in the subsequent process.